Punch for perforating sheet metal



Sept. c SCULL PUNCH FOB PERFORATI NCY SHEET NETAL INVENTOR Chester Scull Filed Jan. 3, 1940 Patented Sept. 10, 1940 UNITED STATES PATENT OFFICE Chester Scull, ward G. Bu

Philadelphia, Pa., assignor toEddd Manufacturing Company,

Philadelphia, Pa., a. corporation of Pennsylvania Application January 3, i940, Serial No.

This invention in general and more particularly to a 9Claims.

relates to punches punch designed and adapted for perforating special alloy metal such as stainless steel.

The principal object of the invention is to provide an improved punch of a design and construction adapted to facilitate the clean cut perforation of sheet metal and to retain the sharpness of its cutting face over comparatively long periods of time.

Another object of a sheet metal punch of the the invention is to provide kind indicated, and

having an improved arrangement of perforating instrumentalities upon its cutting face.

A further object is to provide a punch suitable for perforating sheet metal,

face

such as steel, and

of a type particularly adapted to cleanly and effectively perforate such metal and be capable of ready retraction from the aperture created thereby.

With these and other obj ects not specifically referred to, the invention resides in the combination and arrangement and in the detail of construction as hereinafter be best understood set forth, and will when taken in connection with the accompanying drawing wherein:

Fig. 1 is a sectional view, disclosing a punch partly in elevation,

embodying the invention, and

operatively retained in a punch head in position to perforate material on an adjacent anvil;

Fig. 2is a perspective view of the punch; Fig. 3 is a bottom plan view of the cutting face of the punch;

Fig. 4 is an enlarged, fragmentary, longitudinal sectional view, taken on the line and as viewed in the direction of the arrows Fig. 5 is a view similar to line and as viewed in the direction rows 5-5 of Fig. 3.

4-4 of Fig. 3; and Fig. 4, taken on the of the ar- Referring now to the drawing'wherein similar characters of reference parts in the several views of of the invention, punch head or ind 5 power press, and B a punch tures of the present invention and adapted to be operatively secured in the punch head A. The

material to be operated upon,

stance, a sheet of steel 9, is or die C having the stem of the punch A and terial.

icate corresponding the preferred form the letter A designates the holder of a conventional type embodying the feain the present inplaced'on an anvil hole In which receives the the perforated ma- The punch B, which is preferably composed of steel, comprises an enlarged shank H, having a recess I! which accommo dates the set screw means (not shown) of the by which the punch is secured to the latter. The shank H has an annular flange or shoulder 13 the upper surface of which is adapted to normally seat against the bottom of the punch head (Fig. 1), while the bottom of the said flange is tapered as-at ll, and merges smoothly into the stem H) which terminates in a hardened cutting or shearing face, designated generally at D. 10

The design and general mechanical principles of the cutting face D which embodies the distinctive features of this invention, may be better understood by considering the said cutting face as being divided into two halves by either 15 of the sectional lines 4-4 or 5-5 of Figure 3. The half, for example, on the lower side of the sectional line 5-5, has a smoothly shelving or sloping surface in angular relation to the vertical axis of the stem Hi, this sloping surface be- 2() ing defined by a sector S which is circumscribed by the radii l6, l1 and their subtended arc l8, which'latter forms one of the two comparatively large, angularly-positioned, arcuate cutting or shearing edges of the cutting face D. The re- 25 maining portion of this half of the cutting face D is occupied by a smaller sector or facet S the surface of which lies in a plane angularly positioned with respect to the plane of the larger sector S and with respect to the vertical axis of 30 the stem l5 of the punch. The plane surface of the facets is defined by the common radius H, the radius I9 and the comparatively small arc 2|, the latter forming an auxiliary or second shearing or cutting edge which coacts with the 5 cutting edge or are l8 to complete one-half of the shear of the material to be cut; the shearing of the other half being effected by a similar arrangement of sectors with corresponding shearing edges on the other half of the cutting face D now to be described.

The other and similar half of the cutting face D as indicated above, has a sloping surface in angular relation to the vertical axis of the stem l5, as defined by the sector T which is circumscribed by the common radius [9, the radius 22, and the subtended are 23, the latter forming the other large, angularly-arranged, arcuate cutting edge of the cutting face of the punch. The remaining surface of the instant half of the cutting face, as in the other half above-described, takes the form of a small sector or facet '1 whose surface is in angular relation to the vertical axis of the stem and. to the plane of the larger sector T. The facet T is circumscribed by the two or other fastening punch head A, and

I tinction to common radii, i6, 22 and the small arc or arcuate cutting edge 24. The relative lengths and slopes of the cutting arcs or edges on each half of the cutting face, it is evident, will determine the character and the extent of the progressive cut afforded by each cutting edge.

As best shown in Figs. 2 and 5, the broken line 25 which divides the cutting face into equal halves, and formed by the juxtaposition of the facet S and sector T on one side; and the facet 'I' and sector S on the other side, provides a comparatively sharp, compound ridge or edge, each half of which slopes centrally downwardly to the axis of the stem l5 or the center of the cutting face D where it joins and forms a continuation of the other half. This ridge, which may be considered the dividing line between the two halves of the cutting face, ascends from the said centre or axis to join the junction of the arcs l8, 2| and 23, 24 where, in conjunction with the adjacent facets and sectors, it forms salient points or perforating projections 26, 26' which may be considered as pilots to facilitate the initiation of the progressive cutting or shearing action of the punch in operation.

In practice, the action of the instant punch may be readily comprehended by comparison with a punch having a uniformly flat end. In this latter case, it is evident the pressure essential to perforate the materialwill be applied equally and simultaneously about those portions of its periphery in contact with the punch. In contradisthis action, in the case of the punch B, it will be observed that the pilots or projecting points 26, 26 will initially pierce or form a small hole in the material at diametrically opposite points and with but a fraction of the force required to effect a complete perforation.

This initial piercing action is immediately followed by a partial division or initial slight splitting of the disc of material from the points of initial perforation and in coincidence with the center line or ridge 25 which maintains progressive contact with the material. Simultaneously with this action, a smooth, progressive shearing or cutting action of the larger, arcuate, angularly-positioned cutting edges l8 and 23 from continuously opposite points of the periphery of the cutting. face D, takes place. This last described action is supplemented by the substantially synchronous shearing action of the two facets S and I or small arcs 2| and 24 which complete the cutting of the two comparatively small portions of the material not cut by the larger sectors or cutting edges l8 and 23.

The angle a between the inclined surface S or T respectively and a plane 11 which is perpendicular to the axis a: of the punching tool B, is comparatively small as indicated by Fig. 4 of the drawing. This angle a may be of the order of about 15. The angle b between the plane :11, and the surface '1' or S respectively is considerably greater, as shown in Fig. 1, and it may be of the order of about 50 to 60. The relation between the angles a and b is, therefore, in the order of about 1 to 4. The end view shown in Fig. 3 indicates that the surface S covers a sector which is about five times as great as the sector covered by the adjoining surface portion S The inclination of the surfaces S and T runs parallel to the radial lines I! and 22 respectively, thereby facilitating the grinding of these surfaces. The inclination of the surfaces S and T runs about vertical to the radial lines l9 and I 6 respectively.

The entire operation of perforating a section of material, it is understood, takes but a fraction of a second, but has been herein described as considering the punch as slowly moving, by com paratively small increments, against and through the material,

It may be further pointed out that by reason of the initial piercing and partial splitting of the material and the further progressive action of the present punch, the entire perforating action is facilitated, made smoother and less noisy, the action being markedly conducive to the long life of the punch and the power press, and the general comfort of the operator. In addition to this by reason of the initial splitting of the material alluded to above, the stem of the punch is less prone to bind in the anvil and/or have its shearing blunted, as in punches having uniformly fiat or uniformly concave cutting faces.

It is to be understood that the invention may be embodied in other specific forms without departing from the thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate thescope of the invention; and it will be further understood that each and every novel feature and combination present in or possessed by the mechanism herein disclosed, forms a part of the invention included in the application.

What I claim is:

1. A punch of the character described, comprising, in combination, a body portion, a cutting face arranged on one end of the body portion, a median line dividing the cutting face into two halves, each of said halves being similar and having a pair of cutting instrumentalities, one of the instrumentalities having a comparatively long arcuate edge, the other cutting instrumentality having a comparatively short arcuate edge, and a ridge coincident with the median line and serving as a piercing agency independently of the arcuate cutting edges.

2. A punch of the character described, comprising, in combination, ranged on an end of the stem and having two similar half portions, each of the half portions including a pair of coacting surfaces, one of the surfaces being a comparatively large sector of the half portion, the other of the surfaces being a comparatively small sector of the half portion, cutting means arranged on both of said surfaces and piercing means arranged on a median line dividing the two half portions.

3. A punch of the character described comprising, in combination, a cylindrical member, a cutting face arranged on an end of the member, a pair of cutting means arranged on each half portion of the said face, one of said cutting means having an arcuate edge whose plane is arranged in substantial angular relation to the axis of the said member, and having a second arcuate edge whose plane is positioned in angular relation to the first mentioned arcuate edge and to the said axis, and piercing means common to both of said half portions and arranged therebetween.

4. A punch of the character described and wherein each half of the cutting face of the punch progressively completes one-half of a perforating operation, comprising an elongated member, a cutting face arranged on an end of the member and having a pair of bevelled surfaces on each half portion thereof, said surfaces being angulara stem, a cutting face ar-' spirit or essential attributes 1y positioned with respect to each other and inclined relatively to the vertical axis of the member, one of the bevelled surfaces providing a comparatively long arcuate cutting edge, the other of the surfaces having a comparatively short arcuate cutting edge, and piercing means common to the bevelled surfaces of both of said half portions and ,adapted to facilitate the initiation and progress of a perforating operation.

5. In a tool for punching holes, a shank, a cutting edge at one end of said shank and along the outer surface thereof, said cutting edge comprising adjoining portions which are oppositely inclined relative to the axis of said shank, one of two such adjoining portions being comparatively slightly inclined relative to a plane which extends perpendicular to the axis of said shank, and the other portion being considerably more inclined relative to such plane.

6. In a tool for punching holes, a shank, the outer surface of said shank which is coextensive with the axis thereof, and one of the end surfaces of said shank forming together a cutting edge, said end surface comprising pairs of portions which are inclined relative to a plane which extends perpendicular to the axis of the shank, the relation between the inclination angles of the two surface portions of one pair being in the order of about 2 to 7.

7. In a tool for punching holes, a shank, the outer surface of said shank which is coextensive with the axis thereof, and one of the end surfaces of said shank forming together a cutting edge, said end surface comprising pairs of portions which are inclined relative to a plane which extends perpendicular to the axis of the shank, the inclination angles of the portions of a pair of surface portions being in the order of about 15 and respectively.

8. In a tool for punching holes, a shank adapted to be moved in the direction of its axis, the outer surface of said shank which is coextensive with the axis thereof and one of the transverse end surfaces of said shank forming together a cutting edge, said end surface comprising pairs of adjoin ing surface portions, one surface portion of such pair being inclined in one direction relative to the axis of the shank, and the second surface portion of the same pair being inclined relative to the axis of said shank in another direction, the directions of inclination of the surfaces including an angle of less than when viewed in the direction of the axis.

9. In a tool for punching holes, a shank adapted to be moved in the direction of its axis, the outer surface of said shank which is coextensive with the axis thereof and one of the transverse end surfaces of said shank forming together a cutting edge, said end surface comprising pairs of adjoining surface portions, one surface portion of such pair being inclined in one direction relative to the axis of the shank, and the second surface portion of the same pair being inclined relative to the axis of said shank in another direction, the directions of inclination of the surfaces including an angle of about the order of 90 when viewed in the direction of the line of intersection of two surface portions belonging to one pair.

CHESTER SCULL; 

